class Solution110 {
//    public boolean isBalanced(TreeNode root) {
//          if(root == null) return true ;
//          return isHight(root) >= 0;
//    }
//    private int isHight(TreeNode root){
//          if(root == null ) return 0 ;
//          int leftH = isHight(root.left) ;
//          int rightH = isHight(root.right);
//          if(leftH>=0&&rightH>=0 &&Math.abs(leftH - rightH) <= 1) return Math.max(leftH , rightH)+1 ;
//          return -1 ;
//    }
}